1. Field of the Invention
The methods and equipment of the invention are adapted to the precise measurement of perpendicularity of a rotational axis relative to a reference line. A collimated light source is rotated about an axis and the minimum distance from the light beam relative to the reference line is measured at two or more points. The non-perpendicular angle can be calculated using these distances and the position of the points and rotational axis.
The reference line is defined by points on a string or by visual targets.
The rotational axis of the collimated light source can be mounted on a base. If the edges of the base are aligned with the rotational axis of the collimated light source, the base edge angle relative to the string can be measured. If the base edge is aligned with another object, the object's angular orientation relative to the string can also be measured.
The alignment device can be easily adapted to measure the alignment of objects such as rolls, foundation bolts, structures, and processing equipment found in any industry. Surveyors, for example, will find this device very useful for a large number of important alignment measuring operations. This device is especially useful where the alignment of a number of objects relative to a common reference line such as a string need to be measured. It is also useful where the alignment of an object needs to be repeatedly measured relative to a fixed reference line, such as when the object is installed and needs to be correctly aligned.
2. Discussion of the Prior Art
The most common alignment method involves the use of surveyor methods and instruments that are oriented to an offset reference line. A survey transit, for example, is aligned to a reference line using suitable targets or markers. The transit is then rotated 90 degrees establishing a line of sight that is perpendicular to the offset reference line. A ruler is placed on at least two points of the item to be measured and the difference in ruler readings indicate how far out of alignment the item is (i.e. non-perpendicular to the offset reference line).
The accuracy of this method has been improved by using lasers, specialized optical instruments, and electronic enhancements of the appropriate surveyor equipment. However, the more accurate devices often require a lot of time to obtain the desired measurement. There can be measurement accuracy problems when the item to be measured is behind obstructions requiring the need for specialized reference setups and fixtures.
U.S. Pat. No. 5,430,539 provides for the measure of the relative alignment of two body axes for parallelism with a laser beam to fixed, electronic targets. However, this method has a number of limitations. The fixed targets create an electronic signal that requires a computer to solve a series of linear equation system with a number of equations. The alignment measurement is only relative between two body axes. There is no method disclosed for an easy, simple method for calculating alignment relative to a fixed reference line. Also, the targets must be spaced nearby the two body axes to be measured. The measurement of a large number of body axes in a processing line would require a large number of accurately placed electronic detectors. These limitations greatly reduce the practical application of this method.